1. Field of the Invention
The present invention relates to a copying apparatus for automatically feeding documents and punching or binding a predetermined number of copies.
2. Description of the Prior Art
In recent years, various recording apparatuses such as printers and facsimile apparatuses are widely used in various fields as well as copying machines. Of these recording apparatuses, a copying machine tends to have high operation speed and multifunctions. An apparatus for forming a large number of copies using a copying machine and sorting, automatically punching, or folding the copies has been proposed (e.g., Japanese Patent Laid-Open (Kokai) Nos. 61-94180 and 61-84662, and Journal of Electrophotography Society Vol. 24, No. 3 (1985), pp. 188 to 194). In order to record a large number of documents to be recorded at high speed, a circulating type automatic document feeder as disclosed in Japanese Patent Application No. 62-12201 can be combined with a copying machine. In this case, a copying speed is preferably increased as much as possible.
In a conventional exposure method wherein a document is fixed in position and an optical system is moved, a moving distance and moving speed of the optical system is changed in accordance with a copying paper size and a copying magnification, thereby increasing a copying speed. However, an automatic document feeding type copying apparatus to which the present invention is applied performs sync exposure wherein an optical system is fixed in position, and a photosensitive body is synchronously moved while circulating a document. Therefore, in a variable magnification mode such as an enlargement or reduction mode in which a copying speed is determined on the basis of a copying paper size and a copying magnification like in a conventional apparatus, a copying operation may sometimes be disabled.
On the other hand, a copying apparatus which has a function of copying two one-side documents on both front and back surfaces of a copying paper sheet and copying a document having images on both surfaces on one surface of each of two copying paper sheets has also been proposed.
A copying apparatus having many functions described above also has a binding margin forming function since a binding margin is preferably formed on one side of a copy when a set of copies is to be punched or bound. When one-side documents are copied on both the surfaces of a copying paper sheet, binding margins are formed on opposite sides on the front and back surfaces of a copy. For this reason, an image forming position upon formation of an image may be shifted. Image shift can be realized by controlling a paper feed timing of a copying paper sheet with respect to an image formed on a photosensitive body. In order to form binding margins on the same side of the front and back surfaces of a copying paper sheet, image shift need only be performed when an image is formed on either the front or back surface.
Meanwhile, both-side copies which are subjected to punch or binding processing and are delivered from a processing apparatus are preferably stacked in the order of pages from the above.